As an EmbeddedChat developer

I need to:
integrate EmbeddedChat with the new Rocket.Chat native Matrix homeserver while keeping direct access to Rocket.Chat as an alternate option.

So That:
EmbeddedChat can work with any Matrix or Rocket.Chat server, benefit from federation across the wider Matrix network, and avoid much of the complexity found in the previous direct integration approach.

Acceptance Criteria

• Check out the Matrix home server for Rocket.Chat: https://github.com/RocketChat/homeserver
• EmbeddedChat has a configuration option to choose between using the native Matrix homeserver and direct Rocket.Chat access.
• When configured to use the native Matrix homeserver, EmbeddedChat can connect to a single configured channel, join it, and send and receive messages successfully.
• Documentation is added explaining how to configure EmbeddedChat for the native Matrix homeserver and how to switch between Matrix and direct Rocket.Chat modes.